Copper adsorption as a function of solution parameters of variable charge soils

Abstract

Os efeitos do pH e da força iônica (I) sobre a adsorção de cobre (Cu) e a força direcional da reação em solos com cargas variáveis foram avaliados a partir de experimentos tipo "batch". Os resultados foram ajustados pelo modelo de Langmuir e, de acordo com as isotermas de adsorção, a afinidade de Cu (K L ) foi maior nas amostras do subsolo (0,061-0,468 L kg -1 ) do que na camada superficial (0,169-0,359 L kg -1 ). A adsorção máxima variou de 1114-2422 mg kg -1 (superfície) a 1002-1334 mg kg -1 (subsolo). Foi observada forte dependência da adsorção de Cu em relação ao pH nas amostras do subsolo, com nítido aumento da retenção de Cu (20-90%) no intervalo de pH do solo entre 4,0-5,0. A adsorção de Cu foi alterada pelo aumento da I e indicou diferentes mecanismos (esferas interna e externa) de retenção do metal. A reação foi favorável e espontânea, conforme indicado pelos valores negativos da variação da energia livre ( G) e pelo fator de separação K R < 1. A interface solo-solução e a adsorção de Cu foram termodinamicamente descritas por uma abordagem teórica. Adsorption reaction was favorable and spontaneous, as indicated by negative values of the free energy variation ( G) and the separation factor K R < 1. Soil-solution interface and Cu adsorption were also thermodynamically described by a theoretical approach. Effects of pH and ionic strength (I) on copper (Cu

Biochar application to metal-contaminated soil: Evaluating of Cd, Cu, Pb and Zn sorption behavior using single- and multi-element sorption experiment

“…Soil pH decreases at increased metal concentrations during single-and multi-element sorption can be attributed to the hydrolysis effect and release of H + from soil sorption sites (Ponizovsky et al 2007, Mouta et al 2008. As adverted in Figure 4, pH decrease during single-element sorption at equilibrium was the most pronounced for Cu and followed the order Pb > Zn > Cd.…”

Nickel adsorption by variable charge soils: effect of pH and ionic strength

“…In both cases, adsorption reactions can be described mathematically by determining the Gibbs free energy (Silveira et al, 1999;Dias et al, 2003;Soares et al, 2005;Casagrande et al, 2008;Mouta et al, 2008;:…”

“…The Langmuir isotherm, fitted by nonlinear models, was successfully applied in the study of metals in Oxisols, including Ni (Camargo et al, 1989;Pombo et al, 1989). However, metal adsorption modeling in tropical soils is rarely accompanied by a more detailed description, based on thermodynamics concepts (Silveira et al, 1999;Dias et al, 2003;Soares et al, 2005;Iglesias et al, 2007;Casagrande et al, 2008;Mouta et al, 2008;. Some information has been obtained on thermodynamic modeling for the adsorption reaction of some metallic ions by homogeneous surfaces, such as kaolinite and oxidic interfaces (James and Healy, 1972;Angove et al, 1999;Trivedi and Axe, 2000), but there are few data on the thermodynamics of the Ni adsorption reaction in the soils (Sen Gupta and Bhattacharyya, 2006).…”

Nickel adsorption and desorption in an acric oxisol as a function of pH, ionic strength and incubation time

“…In addition, the difference between the PZSE values of the soil samples studied by Moreira et al (2008) was similar to that observed in this study, supporting the above hypothesis. According to the results of Silveira and Alleoni (2003), Casagrande, Soares and Mouta (2008), Mouta, Soares and Casagrande (2008), and Soares, Casagrande and Mouta (2009), the higher amounts of metals adsorbed in topsoil horizons are correlated to the organic matter content. Soil organic matter may be responsible for 50 to 95% of the cation exchange capacity (CEC) in Brazilian Oxisols, whose inorganic fraction is predominantly composed by low reactive minerals Alleoni, 2008).…”